Low noise, low distortion, complementary IF amplifier

Abstract

Arrangements of Class AB (push-pull) amplifiers, one in a higher voltage configuration and one in a lower voltage configuration, to achieve a high intercept at low power as well as a low noise figure in a complementary technology allowing for higher performance at lower power. In an illustrative embodiment, the invention includes a first circuit for receiving an input signal; a second circuit for shifting a level of the input signal; and a third circuit for amplifying the input signal. In the illustrative embodiment, the third circuit includes first and second transistors Q 3 and Q 4 connected in a push-pull configuration. In the illustrative embodiment, the first and second transistors Q 3 and Q 4 are connected to form Class AB amplifiers and the first transistor Q 3 is of a first type and the second transistor Q 4 is of a second type. The teachings of the present invention are illustrated in a differential amplifier.

What is claimed is:  
     
       1. An amplifier comprising: 
       first means for receiving an input signal;  
       second means for shifting a level of said input signal; and  
       third means for amplifying said input signal, said third means including first and second transistors Q 3  and Q 4  connected in a push-pull configuration, wherein said first transistor Q 3  is of a first type and said second transistor Q 4  is of a second type and said first and second transistors Q 3  and Q 4  being connected whereby an output terminal of said first transistor Q 3  is connected to an output terminal of said amplifier and an output terminal of said second transistor Q 4  is connected to an output terminal of said amplifier;  
       wherein said second means includes a third transistor Q 1  of said second type and a fourth transistor Q 2  of said first type, and wherein an output terminal of said third transistor Q 1  is connected to ground via a first current source, and further wherein the output terminal of said third transistor Q 1  is connected to an input terminal of said second transistor Q 4 .  
     
     
       2. The invention of  claim 1  wherein said first and second transistors Q 3  and Q 4  are connected as Class AB amplifiers. 
     
     
       3. The invention of  claim 1  wherein an input terminal of said third transistor Q 1  is connected to said output terminal of said amplifier via a resistor R F . 
     
     
       4. The invention of  claim 3  wherein said input terminal of said third transistor Q 1  is connected to an input terminal of said fourth transistor Q 2 . 
     
     
       5. The invention of  claim 4  wherein an output terminal of said fourth transistor Q 2  is connected to an input terminal of said first transistor Q 3 . 
     
     
       6. The invention of  claim 5  wherein said output terminal of said fourth transistor Q 2  is connected to a source of supply voltage V cc  by a second current source I 2 . 
     
     
       7. The invention of  claim 6  wherein a terminal of said first transistor Q 3  is connected to said source V cc  by a third current source I 3 . 
     
     
       8. The invention of  claim 7  wherein a terminal of said second transistor Q 4  is connected to ground via a fourth current source I 4 . 
     
     
       9. The invention of  claim 1  wherienf said first type is PNP and said second type is NPN. 
     
     
       10. The invention of  claim 1  wherein said first type is NPN and said second type is PNP.